Today, communication systems such as communication systems that implement LTE (e.g., a LTE system) use various spectrums such as a licensed spectrum, an unlicensed spectrum, a dynamic spectrum, a shared spectrum, or a combination of these spectrums. For example, an entrant may not have access to a licensed spectrum and, instead, may deploy a LTE system in a shared spectrum such as TV White Space (TVWS) or Industrial, Scientific, and Medical (ISM) bands. Such a spectrum may be broad and may include large numbers of channels often occupied by other technologies that make network discovery challenging. Since channels are shared with other operators and other radio access technologies (RATs), such channels are often polluted with localized interferers such as controllable and uncontrollable interferers. Additionally, the availability of such channels often changes over a short period. Accordingly, a LTE system and the bands associated with the LTE system may often have to be reconfigured. These reconfigured bands may be referred to as a dynamic and shared spectrum. Unfortunately, cells such as small cells deployed in a dynamic and shared spectrum may not be able to anchor the LTE system to a licensed spectrum. As a result, mobility management may be a challenge, and the LTE system may need to support both uplink and downlink.
To support the uplink, a random access procedure and/or channel, such as a random access channel (RACH), may be used. Unfortunately, wireless transmit/receive units (WTRUs), such as user equipment (UE), and interferences associated therewith, such as secondary WTRUs and interferences that may be used in a communication system, may provide a number of problems for a random access procedure. For example, RACH preamble transmissions may not be recoverable, as a result of uncontrollable interference (UL transmission). As an example, a WTRU may poorly estimate path loss due to uncontrollable interference (DL transmission), resulting in excessive transmit power for a RACH preamble and potential interference to other RACH transmissions from the same cell. As an example, current RACH techniques have gaps to take into account timing uncertainty, and such gaps may be a problem in that they may allow secondary user transmissions time to access the dynamic and shared spectrum. For LTE standalone solutions using, for example, a coexistence gap mechanism, a RACH capacity may not be enough to support all IDLE mode WTRUs (e.g., where the dynamic and shared spectrum is narrow, as is the case in TVWS, where the spectrum allows for a maximum LTE carrier bandwidth of 5 MHz). Also, for LTE standalone solutions, the coexistence gap mechanism may interfere with the LTE random access procedure (e.g., a Release 10 random access procedure) that may have timing requirements that permit operation of the 6 TDD UL/DL configurations including the random access response window (e.g., a window during which the WTRU expects a response for its random access preamble transmission) that may not be received.